Add DM support, friend identification, and target pruning

React in 1:1 DMs alongside servers/groups, surface the resolved friend
username at startup and in the stats panel, verify reactions actually
stick after adding them (with jump links for manual spot-checking),
and prune stale targets from stats on each run so only the currently
mutual set is shown.

bot/storage.py

@@ -6,7 +6,7 @@ from typing import Optional
 SCHEMA = """
 CREATE TABLE IF NOT EXISTS targets (
     target_id      TEXT PRIMARY KEY,
-    target_type    TEXT NOT NULL CHECK(target_type IN ('guild','group_dm')),
+    target_type    TEXT NOT NULL CHECK(target_type IN ('guild','group_dm','dm')),
     name           TEXT,
     first_seen_at  TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
     reaction_count INTEGER NOT NULL DEFAULT 0
@@ -55,6 +55,28 @@ class Storage:
         if "message_created_at" not in columns:
             self._conn.execute("ALTER TABLE reactions_log ADD COLUMN message_created_at TEXT")
 
+        # Older DBs created before 'dm' targets (1:1 DMs) existed have a CHECK
+        # constraint that only allows 'guild'/'group_dm' — rebuild the table
+        # with the wider constraint, preserving all existing rows.
+        targets_sql = self._conn.execute(
+            "SELECT sql FROM sqlite_master WHERE type='table' AND name='targets'"
+        ).fetchone()
+        if targets_sql and "'dm'" not in targets_sql["sql"]:
+            self._conn.executescript(
+                """
+                ALTER TABLE targets RENAME TO targets_old;
+                CREATE TABLE targets (
+                    target_id      TEXT PRIMARY KEY,
+                    target_type    TEXT NOT NULL CHECK(target_type IN ('guild','group_dm','dm')),
+                    name           TEXT,
+                    first_seen_at  TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
+                    reaction_count INTEGER NOT NULL DEFAULT 0
+                );
+                INSERT INTO targets SELECT * FROM targets_old;
+                DROP TABLE targets_old;
+                """
+            )
+
     def upsert_target(self, target_id, target_type: str, name: str) -> None:
         with self._lock, self._conn:
             self._conn.execute(
@@ -66,6 +88,21 @@ class Storage:
                 (str(target_id), target_type, name),
             )
 
+    def prune_targets(self, keep_target_ids: list) -> int:
+        """Remove targets not present in the latest discovery run (e.g. a server
+        that's no longer mutual, or a stale entry from an earlier bug/test run).
+        reactions_log/channel_scan_state rows are left alone for history/undo."""
+        keep = [str(t) for t in keep_target_ids]
+        with self._lock, self._conn:
+            placeholders = ",".join("?" * len(keep)) if keep else None
+            if placeholders:
+                cur = self._conn.execute(
+                    f"DELETE FROM targets WHERE target_id NOT IN ({placeholders})", keep
+                )
+            else:
+                cur = self._conn.execute("DELETE FROM targets")
+            return cur.rowcount
+
     def has_reacted(self, message_id, emoji: str) -> bool:
         with self._lock:
             cur = self._conn.execute(